A 22-year-old man who came to their aid was also allegedly assaulted, and a 31-year-old woman was allegedly pushed and spat on.

The three children spent the night in custody after the alleged assault. Picture: Bill HearneBoth Sydney Trains employees were treated for minor injuries, and the 22-year-old man sustained small cuts and head bruising.

The 15-year-old boy was charged with being armed with intent, breaching bail, affray, common assault, larceny and transport offences to face Sutherland Local Court on Wednesday.

The 13-year-old boy was charged with two counts of larceny, affray, two counts of common assault, offensive behaviour and drinking alcohol in a public area.

The 14-year-old girl was charged with affray, common assault, offensive behaviour, interfering with the safety of others and attempting to travel on public transport without a valid ticket.

The younger children received conditional bail to face Sutherland Local Court on September 5.